Cavity-resonator tube and associated circuit



Dec. 4, 1951 G. DIEMER CAVITY-RESONATOR TUBE AND ASSOCIATED CIRCUIT Filed y 2 1947 L CL MAMA

l N V EN TOR, azsuvvs D nil Patented Dec. 4, 1951 UNITED STATES PATENT OFFICE CAVITY-RESONATOR TUBE AND ASSOCIATED GIRGUI'I Gsinus 'Di'eine f, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application July 25, 1947, Serial so. 763,681 .In the Netherlands August 22, 1946 (01. sis-6) '5 Claims.

The invention relates to circuit-arrangements for transmitting or generating ultra high-freqnency electrical oscillations 3 in.) which comprise a discharge tube having at least a cathode, a control grid (having a negative potential with respect to the cathode or a potential only slightly different from the cathode potential'), an electrode (anode) having a positive potential with respect to the cathode and a secondary-emission electrode in this sequence the oscillations to be transmitted or oscillations derived from the electrical oscillations generated being supplied to the control grid.

It is'lmown to use a capacitative feed-back from the secondary-emission electrode to the control grid in the above-mentioned circuitarrangemcnt, at "least so far as the latter concerns the generation of oscillations.

, However, this circuit-arrangement exhibits the disadvantage that the capacity which, ,dueto the presence of the tube is connected in parallel with the oscillatory circuit or circuits used, is comparatively high.

The invention provides a circuit-arrangement or the kind mentioned in the preamble, in which this capacity is materially lower.

According to the invention, the control grid and" the anode are interconnected through a path which exhibits a small impedance, at least for the frequency range of the oscillations genera-ted or required to be transmitted. The control grid and the anode are preferably intercom nected by means of a capacity.

'In this case care should be taken to ensure that the-conductors leading from the electrodes to the capacity have a minimum self-induction.

This may, :for example, be realized by providing the capacity within the tube. The electrodes .are preferably constructed in the form of discs. 33y suitably dimensioning the discs and their relative distance it is possible to make the natural capacity between control grid and anode so .high that itiiszno longer necessary to provide an additional capacity between these electrodes.

:In many cases it is advisableito connect the electrodes, at least for high-frequencies, .to a point of constant or substantially constant potential (earth).

As a rule, the voltage of the secondary-emission electrode is chosen to be :lower than that of the anode. The voltage of the secondary emission electrode may, for example, :be comprised between 100 and 1000 volts.

In order that the invention may be-moreclear- 1y understood and readily carriedzinto effect, ,it

. 2. will now be explained more fully with reference to the accompanying drawing, in which a few embodiments are shown by way of example;

Fig; 1 is a schematic circuit diagram of a preferred embodiment of the invention,

Fig. 2 is a schematic circuit diagram of another preferred embodiment of the invention,

Fig. 3 is a schematic circuit diagram of still another embodiment of the invention, and

Fig. 4 is a cross sectional view of the structure forming yet another embodiment of the invennon.

Referring to Fig. 1, l designates a tetrode comprising a cathode 2, a control grid 3,-an anode 4 and a secondary-emission electrode 5. Between the cathode 2 and the control grid 3 is provided an input oscillatory circuit 6 formed by an inductance i and the zero-capacity parallel to this inductance. This zero-capacity is substantially formed by the tube capacity. An output oscillatory circuit 8 of a construction similar to that of the input oscillatory circuit 6 located in between the anode 4 and the second-'- ary-em'ission electrode 5. The inductance 9 forming part of the output circuit 8 may, for

example, be coupled with the inductance -l of the input oscillatory circuit "6. If the system is used for the amplification of oscillations it is more favourable to omit this coupling. The negative resistance which, under certain =condi-" tions may occur between the electrodes 4 and 5 .has a damping-reducing effect on the circuit 8'; if the system is used as an amplifier, the circuit 8 is at any rate required to be damped to such an extent that oscillation is avoided. However, if the :system is utilized as an oscillator, use may be made of the presence of this negative resistance.

Fig. 1 vfurther illustrates the manner in which the direct current voltages are supplied to the several elements of te'trode :l. A voltage source 20 "is provided whosepositive terminal is connected through a radio frequency choke M to anode :4 and whose, negative terminal is connected through resistor IE to grid Secondary.- emission electrode .5 :is connected to a radio frequency choke 15 to a first point intermediate the end terminals in source 2-0, while cathode 4-2 is connected through a radio frequency choke Hi to ansecondpoint intermfidiate the first point. and the negative terminal. Thus :anegative bias is imposed on grid 3., while the magnitude of positive potential impressed .on anode Al exceeds that on'secondary-emission electrode :5. .A block ing condenser :I I is interposed-between secondary mentioned known system such a construction is impossible.

According to the invention, the control grid 3 and the anode 4 are interconnected by means of a condenser it! which has a capacity such that the path of connection between the control grid 3 and the anode 4 exhibits, at least for the frequency range of the oscillations generated or required to be transmitted, a small impedance.

If the said frequency range extends between 30,000 and 300 mc./s., the value of the capacity I may lie between 5 and 100 micro-microfarads, the highest value of the frequency corresponding to the lowest value of the capacity.

The connecting capacity [0 must at any rate have an admittance which, at least for the frequency range referred to, is small with respect to the tube admittances.

In order to ensure satisfactory operation of the system it is desirable that the anode voltage should exceed the voltage of the secondaryemission electrode. The grid-shaped anode 4 is preferably constructed in such manner that the wires, beams or plates from which this anode is built-up, are located, viewed from the cathode, in the shadow of the corresponding wires, beams or plates of the control grid 3. With the use as an oscillator it often sufiices if anode and control grid each have a single aperture, said apertures being located in line.

. In the system shown in Fig. 1 the input oscillatory circuit 6 has connected in parallel with it almost exclusively the control grid-cathode capacity of the tube I, whereas the output oscillatory circuit 8 has solely connected in parallel therewith the anode-secondary emission electrode capacity. In the above-mentioned known system in which the secondary-emission electrode is capacitatively back-coupled to the control grid, the anode and the cathode are capacitatively connected ,to one another and the oscillatory circuit serving to generate the oscillations is arranged between the anode and the secondary-emission electrode, there is, on the contrary, in parallel with this circuit the sum of the capacities: control grid-cathode capacity I control grid-anode capacity anode-secondary emission electrode capacity. In the system according to the invention the zero-capacity is, consequently, materially lower. This is of particular importance if it is desired to generate or to amplify by means of the system oscillations of minimum wavelength.

In generating oscillations the two circuits are inductively coupled with one another, the secondary-emission electrode and the cathode oscillating in this case in opposite phases.

The present system exhibits the further advantage that the damping exerted by the tube on the input oscillatory circuit is more favourable for definite frequency ranges lying in the ultra-shortwave range than in the known system.

Fig. 2 shows a circuit-arrangement which roughly corresponds to that of Fig. 1. This circuit-arrangement is particularly suitable for generating oscillations. It comprises only one oscillatory circuit ll provided between the oathode 2 and the secondary-emission electrode 5 and formed by the inductance l2 and the zero-capacity in parallel therewith, which substantially is constituted by the series-connected tube capacities control grid-cathode capacity and anodesecondary emission electrode capacity. Consequently, with this system the tube capacity connected in parallel with the circuit is as low as possible.

Direct current voltages are supplied to the elements of tetrode I in Fig. 2 in the same manner as illustrated in the circuit of Fig. 1.

In a practical case the circuit I I may be formed by a telescopic Lecher system provided between the secondary-emission electrode and the oathode, as is shown in detail in Fig. 3. The open Lecher system 18 has an electrical length of /2 the high-frequency choke coils l5 and I6 are connected to the Lecher system at an electrical distance of 4X, reckoning from the electrodes concerned. The actual distance between the connecting points of the high-frequency coils and the electrodes is, of course, as a rule less than The separating condenser ll of Figure 2 can be omitted in this case.

With this circuit-arrangement it is desirable to construct the tube in such manner and, consequently, to ensure between the tube capacities: control grid-cathode capacity and anodesecondary emission electrode capacity a ratio such that both the control grid-cathode space and the anode-secondary-emission electrode space are completely controlled.

In a practical embodiment of a tetrode suitable for the present circuit-arrangement care should preferably be taken that the distance between the cathode and the secondary-emission electrode and consequently the transit time of the electrons is minimal. This can be achieved, for example, by constructing the anode and the control grid in the form of parallel metal discs, which exhibit, opposite the cathode, one or more apertures and this preferably in such manner that, viewed from the cathode, the apertures are aligned. If the metal discs are arranged with a sufficiently small relative spacing they may constitute themselves the capacity It).

Fig. 4 is a sectional view of an ultra-high frequency generating structure incorporating a tetrode of the type disclosed in the preceding figures. The tetrode is connected in a circuit electrically equivalent to that of Fig. 1, except for the fact that the input and the output oscillatory circuits 6 and 8 are formed by a pair of cylindrical cavity resonators having a common end wall rather than by lumped inductances and capacitances. Cathode I, grid 3, anode 4 and electrode 5 are of coplanar construction, anode l and grid 3 being formed by parallel metal discs having aligned apertures. The spacing between discs is small and a dielectric is interposed therebetween to define the internal capacity [0. The disc shaped terminal of anode 5 is capacitively coupled to one end wall of output resonator 8,

" while the annular-shaped terminal of grid 3 is directly connected to the opposing end wall of output resonator 8 which is common with input resonator 6. The terminal of cathode 2 is capacitively coupled to the other end wall of resonator 6. Inasmuch as high-frequency oscillations do not appear outside of the resonators, radio frequency chokes are omitted in this circuit.

What I claim is:

1. An ultra-high frequency transmission circuit comprising an electron discharge tube having in successive arrangement a cathode, a grid, an anode and a secondary-emission electrode, means providing a. capacity between said grid and said anode whose impedance value is rel-atively low within a predetermined range of oscillations to efiectively interconnect said grid and said anode, means connected to said grid to apply a negative bias to said grid, and means connected to said anode to apply a first positive potential to said anode and connected to said electrode to apply a second positive potential to said electrode, said first potential having a magnitude exceeding said second potential, and input means to supply oscillations to said grid.

2. An ultra-high range transmission circuit comprising an electron discharge tube having in successive arrangement a cathode, a grid, an anode and a secondary-emission electrode, said grid and anode being juxtaposed to provide a capacity therebetween whose impedance value is relatively low Within a predetermined range of oscillations, means connected to said grid to apply a negative bias to said grid, means connected to said anode to apply a first positive potential to said anode and connected to said electrode to apply a second vpositive potential to said electrode, said first potential having a magnitude exceeding said second potential, a first inductance coupled between said grid and said cathode which in parallel with the interelectrode capacity of said grid and said cathode defines an input resonant circuit, and a second inductance coupled between said anode and said electrode which in parallel with the interelectrode capacity of said anode and electrode defines an output resonant circuit.

3. An ultra-high frequency transmission circuit comprising an electron discharge tube having in successive arrangement a cathode, a grid,

an anode and a secondary-emission electrode,

said grid and anode being juxtaposed to provide a capacity therebetween whose impedance value is relatively low within a predetermined range of oscillations, means connected to said grid to apply a negative bias to said grid, means connec'ted to said anode to apply a first positive potential to said anode and connected to said electrode to apply a second positive potential to said electrode, said first potential having a magnitude exceeding said second potential, a first cavity resonator coupled between said grid and cathode to form an input circuit, and a second cavity resonator coupled between said anode and said electrode to form an output circuit.

4. An ultra-high frequency generating circuit comprising an electron discharge tube having in successive arrangement a cathode, a grid, an anode and a secondary-emission electrode, said grid and said anode being juxtaposed to provide a capacity therebetween whose impedance value is relatively low within a predetermined range of oscillations efiectively interconnecting said grid and said anode, means connected to said grid to apply a negative bias to said grid, means connected to said anode to apply a first positive potential to said anode and connected to said electrode to apply a second positive potential to said electrode, said first potential having a magnitude exceeding said second potential, an inductance coupled between said cathode and said electrode which in parallel with the seriallyconnected interelectrode capacities of said tube defines a resonant circuit.

5. An ultra-high frequency generating circuit comprising an electron discharge tube having in successive arrangement a cathode, a grid, an anode and a secondary-emission electrode, said grid and said anode being juxtaposed to provide a capacity therebetween whose impedance value is relatively low at a predetermined oscillating frequency, a half wavelength open-ended transmission line having two conductors, one of which is connected to said cathode and the other of which is connected to said electrode, means to apply a negative bias to said grid, means to apply a first positive potential to said anode, and means to apply a second positive potential to the midpoint of the electrode-connected conductor, said first potential having a magnitude exceeding said second potential.

GESINUS DIEMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,886,990 Van der Pol Nov. 8, 1932 1,995,175 Gill Mar. 19, 1935 2,151,783 Lopp et a1. Mar. 28, 1939 2,173,193 Zworykin Sept. 19, 1939 2,287,845 Varian June 30, 1942 2,294,782 Jacobsen Sept. 1, 1942 2,452,075 Smith Oct. 26, 1948 FOREIGN PATENTS Number Country Date 582,616 Great Britain Nov. 22, 1946 

